DESCRIPTION (Applicant's abstract): Colorectal carcinoma is the most common gastrointestinal malignancy affecting about 160,000 new cases per year in the United States. Survival rates are closely correlated with the stage of cancer at the time of diagnosis. This Phase II (revised) proposal is based on the fact that it is possible to recover colonic cells from human stool and examine them for biomarkers associated with malignant transformation. Our objective is to develop a noninvasive screening test for colon cancer by demonstrating the expression of tumor associated biomarkers on exfoliated colonocytes isolated from stools of patients with colon cancer. This is a cross-sectional observational study of patients undergoing diagnostic colonoscopy at two medical centers: Sinai Hospital in Baltimore and the Walter Reed Army Medical Center in Washington, D.C. The outcome measures are PCR amplicons of CD 44 splice variants and tumor specific variants of carcinoembryonic antigen (CEA). In addition, cell surface carbohydrate motifs linked to tumorigenesis will be examined by flow cytometry using fluorescently labeled plant lectins that are now to be specific ligands. From previous studies we expect to show a high degree of sensitivity and specificity for detection of colon cancer and its precursor polyps using a panel of these biomarkers. As a reference marker Cytokeratin 19 will be amplified, semiquantitatively, by PCR using cDNA generated from mRNA extracted from the cells. Our objective is to develop a standardized kit for the detection of colon cancer, non-invasively, as a cost-effective screening tool.